i68 



FRESH-WATER BIOLOGY 



233 (220) Chromatophore a single equatorial band, with one pyrenoid. Fila- 



ments branched, attached, frequently with a gelatinous cov- 

 ering. Reproduction by zoospores and isogametes. 



Family CHAETOPHORACEAE . . 234 



234 (242) The zoosporangia of the same form as the vegetative cells; the 



larger species usually bearing long hairs. 



Subfamily CHAETOPHOREAE . . 235 



2 35 ( 2 39) Plant attached, differentiated into base and apex 236 



236 (237, 238) Filaments imbedded in a firm, gelatinous matrix, forming a 



spherical or an irregularly branched, ribbon-like thallus 

 attached at the base Chaetophora Shrank. 



Filaments radiating from a common center, usually terminating in a colorless hair; micro- 

 zoospores with two cilia and a pigment spot near the anterior end; macrozoospores also formed. 



FIG. 232. Chaetophora pisiformis Agardh. X 100. 



237 (236, 238) Filaments not imbedded in a firm gelatinous matrix, the 

 branches irregularly placed, of the same size as the principal 

 axis Myxonema Fries. 



(Original.) 



a firm gelatinous 



Plant either several centimeters long, at- 

 tached, or very minute and free, often passing 

 into a palmella condition. Sexual reproduc- 

 tion by means of isogametes with two cilia 

 and a pigment spot; asexual, by zoospores 

 with four cilia, and by akinetes. 



Myxonema is widely distributed, the mi- 

 croscopical forms occurring almost univer- 

 sally on mosses and liverworts in damp local- 

 ities, while the larger forms are frequent in 

 running water. They have been known to 

 completely cover the beds of streams. The 

 smaller forms are microscopical, and can be 

 detected only after portions of the mosses 

 and liverworts are placed in culture and the 

 Myxonema allowed to develop. 



It will then sometimes cover the top of a 

 culture with a thin film of minute plants. 



FIG. 233. Myxonem lubricum Kutzing. a. 

 portion of branch, b. isogometes. c. zoospores. 

 X 285. (Original.) 



